#include <fcntl.h>
#include <stdlib.h>
#include <sys/stat.h>
+#include <sys/uio.h>
#include <time.h>
#include <unistd.h>
void **ret_value,
size_t *ret_size) {
- _cleanup_close_ int fd = -EBADF;
- _cleanup_free_ void *buf = NULL;
- struct stat st;
usec_t begin = 0; /* Unnecessary initialization to appease gcc */
- uint32_t a;
- ssize_t n;
assert(variable);
begin = now(CLOCK_MONOTONIC);
}
- fd = open(p, O_RDONLY|O_NOCTTY|O_CLOEXEC);
+ _cleanup_close_ int fd = open(p, O_RDONLY|O_NOCTTY|O_CLOEXEC);
if (fd < 0)
return log_debug_errno(errno, "open(\"%s\") failed: %m", p);
- if (fstat(fd, &st) < 0)
- return log_debug_errno(errno, "fstat(\"%s\") failed: %m", p);
- if (st.st_size < 4)
- return log_debug_errno(SYNTHETIC_ERRNO(ENODATA), "EFI variable %s is shorter than 4 bytes, refusing.", p);
- if (st.st_size > 4*1024*1024 + 4)
- return log_debug_errno(SYNTHETIC_ERRNO(E2BIG), "EFI variable %s is ridiculously large, refusing.", p);
-
- if (ret_value || ret_attribute) {
- /* The kernel ratelimits reads from the efivarfs because EFI is inefficient, and we'll
- * occasionally fail with EINTR here. A slowdown is better than a failure for us, so
- * retry a few times and eventually fail with -EBUSY.
- *
- * See https://github.com/torvalds/linux/blob/master/fs/efivarfs/file.c#L75
- * and
- * https://github.com/torvalds/linux/commit/bef3efbeb897b56867e271cdbc5f8adaacaeb9cd.
- */
- for (unsigned try = 0;; try++) {
- n = read(fd, &a, sizeof(a));
- if (n >= 0)
- break;
- log_debug_errno(errno, "Reading from \"%s\" failed: %m", p);
- if (errno != EINTR)
- return -errno;
- if (try >= EFI_N_RETRIES_TOTAL)
- return -EBUSY;
-
- if (try >= EFI_N_RETRIES_NO_DELAY)
- (void) usleep_safe(EFI_RETRY_DELAY);
- }
+ uint32_t attr;
+ _cleanup_free_ char *buf = NULL;
+ ssize_t n;
- /* Unfortunately kernel reports EOF if there's an inconsistency between efivarfs var list
- * and what's actually stored in firmware, c.f. #34304. A zero size env var is not allowed in
- * efi and hence the variable doesn't really exist in the backing store as long as it is zero
- * sized, and the kernel calls this "uncommitted". Hence we translate EOF back to ENOENT here,
- * as with kernel behavior before
- * https://github.com/torvalds/linux/commit/3fab70c165795431f00ddf9be8b84ddd07bd1f8f
- *
- * If the kernel changes behaviour (to flush dentries on resume), we can drop
- * this at some point in the future. But note that the commit is 11
- * years old at this point so we'll need to deal with the current behaviour for
- * a long time.
- */
- if (n == 0)
+ /* The kernel ratelimits reads from the efivarfs because EFI is inefficient, and we'll occasionally
+ * fail with EINTR here. A slowdown is better than a failure for us, so retry a few times and
+ * eventually fail with -EBUSY.
+ *
+ * See https://github.com/torvalds/linux/blob/master/fs/efivarfs/file.c#L75 and
+ * https://github.com/torvalds/linux/commit/bef3efbeb897b56867e271cdbc5f8adaacaeb9cd.
+ *
+ * The variable may also be overwritten between the stat and read. If we find out that the new
+ * contents are longer, try again.
+ */
+ for (unsigned try = 0;; try++) {
+ struct stat st;
+
+ if (fstat(fd, &st) < 0)
+ return log_debug_errno(errno, "fstat(\"%s\") failed: %m", p);
+ if (st.st_size == 0)
return log_debug_errno(SYNTHETIC_ERRNO(ENOENT),
"EFI variable %s is uncommitted", p);
+ if (st.st_size < 4)
+ return log_debug_errno(SYNTHETIC_ERRNO(ENODATA), "EFI variable %s is shorter than 4 bytes, refusing.", p);
+ if (st.st_size > 4*1024*1024 + 4)
+ return log_debug_errno(SYNTHETIC_ERRNO(E2BIG), "EFI variable %s is ridiculously large, refusing.", p);
+
+ if (!ret_attribute && !ret_value) {
+ /* No need to read anything, return the reported size. */
+ n = st.st_size;
+ break;
+ }
- if (n != sizeof(a))
- return log_debug_errno(SYNTHETIC_ERRNO(EIO),
- "Read %zi bytes from EFI variable %s, expected %zu.", n, p, sizeof(a));
- }
-
- if (ret_value) {
- buf = malloc(st.st_size - 4 + 3);
- if (!buf)
+ /* We want +1 for the read call, and +3 for the additional terminating bytes added below. */
+ char *t = realloc(buf, (size_t) st.st_size + MAX(1, 3));
+ if (!t)
return -ENOMEM;
+ buf = t;
+
+ const struct iovec iov[] = {
+ { &attr, sizeof(attr) },
+ { buf, (size_t) st.st_size + 1 },
+ };
+
+ n = readv(fd, iov, 2);
+ assert(n <= st.st_size + 1);
+ if (n == st.st_size + 1)
+ /* We need to try again with a bigger buffer. */
+ continue;
+ if (n >= 0)
+ break;
+
+ log_debug_errno(errno, "Reading from \"%s\" failed: %m", p);
+ if (errno != EINTR)
+ return -errno;
+ if (try >= EFI_N_RETRIES_TOTAL)
+ return -EBUSY;
+ if (try >= EFI_N_RETRIES_NO_DELAY)
+ (void) usleep_safe(EFI_RETRY_DELAY);
+ }
- n = read(fd, buf, (size_t) st.st_size - 4);
- if (n < 0)
- return log_debug_errno(errno, "Failed to read value of EFI variable %s: %m", p);
- assert(n <= st.st_size - 4);
+ /* Unfortunately kernel reports EOF if there's an inconsistency between efivarfs var list and
+ * what's actually stored in firmware, c.f. #34304. A zero size env var is not allowed in EFI
+ * and hence the variable doesn't really exist in the backing store as long as it is zero
+ * sized, and the kernel calls this "uncommitted". Hence we translate EOF back to ENOENT
+ * here, as with kernel behavior before
+ * https://github.com/torvalds/linux/commit/3fab70c165795431f00ddf9be8b84ddd07bd1f8f.
+ *
+ * If the kernel changes behaviour (to flush dentries on resume), we can drop this at some
+ * point in the future. But note that the commit is 11 years old at this point so we'll need
+ * to deal with the current behaviour for a long time.
+ */
+ if (n == 0)
+ return log_debug_errno(SYNTHETIC_ERRNO(ENOENT),
+ "EFI variable %s is uncommitted", p);
+ if (n < 4)
+ return log_debug_errno(SYNTHETIC_ERRNO(EIO),
+ "Read %zi bytes from EFI variable %s, expected >= 4", n, p);
- /* Always NUL-terminate (3 bytes, to properly protect UTF-16, even if truncated in the middle
- * of a character) */
- ((char*) buf)[n] = 0;
- ((char*) buf)[n + 1] = 0;
- ((char*) buf)[n + 2] = 0;
- } else
- /* Assume that the reported size is accurate */
- n = st.st_size - 4;
+ if (ret_attribute)
+ *ret_attribute = attr;
+ if (ret_value) {
+ assert(buf);
+ /* Always NUL-terminate (3 bytes, to properly protect UTF-16, even if truncated in
+ * the middle of a character) */
+ buf[n - 4] = 0;
+ buf[n - 4 + 1] = 0;
+ buf[n - 4 + 2] = 0;
+ *ret_value = TAKE_PTR(buf);
+ }
if (DEBUG_LOGGING) {
usec_t end = now(CLOCK_MONOTONIC);
/* Note that efivarfs interestingly doesn't require ftruncate() to update an existing EFI variable
* with a smaller value. */
- if (ret_attribute)
- *ret_attribute = a;
-
- if (ret_value)
- *ret_value = TAKE_PTR(buf);
-
if (ret_size)
- *ret_size = n;
+ *ret_size = n - 4;
return 0;
}
projects / thirdparty / systemd.git / commitdiff
